Cloudiness and marine boundary layer dynamics in the ASTEX Lagrangian experiments. Part I: synoptic setting and vertical structure

Abstract

The Atlantic Stratocumulus Transition Experiment (ASTEX) southeast of the Azores Islands examined the coupled evolution of cloud, dynamical, and thermodynamical vertical structure in a marine boundary layer (MBL) air mass as it advected from cold to warm water in the trade winds. In two "Lagrangian' observation periods during ASTEX, an unprecedentedly complete view of MBL and cloud evolution was achieved by nearly continuous aircraft coverage for 36-48 hours using three boundary layer aircraft, supplemented by satellite, ship, and balloon observations. The authors present the synoptic setting and the evolution of cloudiness as seen from satellite for both Lagrangians, and vertical sections of wind, temperature, mixing ratio, liquid water, droplet concentration, and ozone formed from time series of 17 aircraft soundings during each Lagrangian. -from Authors